Thanks for your reply! I checked the error console (totally forgot about it) and it confirmed my idea. It actually says:

Error: [$injector:modulerr] Failed to instantiate module ionicApp due to:
[$injector:modulerr] Failed to instantiate module API due to:
[$injector:nomod] Module 'API' is not available! You either misspelled the module name or forgot to load it.
If registering a module ensure that you specify the dependencies as the second argument.

enter link description here
So here is a link provided by console.
So the thing is that angular does not see this file. Thats why the problem is ‘how to make angular see some other files’